RU2011264C1 - Method of automatic control of excitation of synchronous generator - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: the method is based on determination of the voltage and frequency deviation and derivatives gains at low wobblings of the generator, increase of the first frequency derivative gain at high wobblings, measurement of the value of rotor, voltage and current fluctuations and at determination of the rotor winding sluggishness according to their relationship and variation of the first frequency derivative in direct proportion to variation of the rotor winding sluggishness. EFFECT: facilitated procedure. 4 cl, 2 dwg

Description

 The invention relates to electrical engineering and can be used to automate the settings of the excitation regulators of powerful synchronous generators.

 The known method (1), based on measuring the average squares of the amplitude of the oscillations of the stabilization parameter in the region of low and high frequencies of an electromechanical nature and generating amplification coefficients for the deviation and derivative of the generator voltage frequency, as integrals of the difference of the average squares in the region of low and high frequencies.

 The known method allows you to quickly adjust the coefficients of the controller in the steady state, however, it does not allow for changing the ratio of the coefficients when changing the modes of the generator and optimal damping of large swings.

 Closest to the essence of the present invention is the method (2), based on measuring the value of the first derivative of the frequency of the voltage of the generator, setting the gain for the deviation and the first derivative of the voltage and frequency for small swings, limiting the value of the first derivative of the voltage and increasing to the maximum realized regulation coefficient according to the first derivative of the frequency upon reaching the first derivative of the frequency of a given value. The disadvantage of this method is the non-optimal choice of the magnitude of the control coefficient for the first derivative of the frequency for both large and small swings, due to the lack of an optimality criterion for the ratio of the control coefficients in deviation and the first derivative of the frequency.

 The aim of the invention is to improve the quality of regulation by ensuring optimal damping of both small and large oscillations of the generator. The purpose of the invention is achieved by measuring the ripple voltage and current of the generator rotor at the frequency of the switching cycles of the valve converter supplying the rotor, determining their ratio proportional to the inertia of the rotor winding, and changing the gain with respect to the first derivative of the generator voltage frequency, is directly proportional to the change in inertia of the rotor winding.

Mathematically, the method can be described as follows:
ΔU _f = -K _0u ΔU _g -K _1u U $\genfrac{}{}{0ex}{}{\text{1}}{\text{g}}$ + K _0f Δf + σf ¹ , (1) where Δ U _f is the change in the excitation voltage
ΔU _g , U _g ¹ - the deviation and the first derivative of the generator voltage frequency.

Δf, f ¹ - the deviation and the first derivative of the generator voltage.

, (2)
ΔU_f, Δ I_f - переменные составляющие напряжения и тока возбуждения на частоте ω_k<218>ω₁-ω₂
ω_k(f_k) - полоса пропускания частот, близких к частоте коммутационных циклов (в трехфазном мостовом преобразователе частоты f_k = 300 Гц).To _ou , To _1u - gain on the corresponding channels To _o f, σ
σ =

, (2)
ΔU _f , Δ I _f - alternating components of voltage and excitation current at a frequency ω _k <218> ω ₁ -ω ₂
ω _k (f _k ) is the bandwidth of frequencies close to the frequency of switching cycles (in a three-phase bridge frequency converter f _k = 300 Hz).

=

, (3) где I_do - постоянная времени в режиме холостого хода генератора (Х_с = ∞ ),
Х_с, Х_d ¹, X_d - индуктивные сопротивления сети переходное и синхронное генератора соответственно.The value of σ determines the inertia of the field winding, the time constant of which is determined from the following relation:
T

=

, (3) where I _do is the time constant in the idle mode of the generator (X _c = ∞),
X _s , X _d ¹ , X _d - inductive resistances of the transient and synchronous generator networks, respectively.

 From formula (3) we see that the inertia time constant of the field winding is affected by the magnitude of the inductive resistance of the network, i.e., the external circuit conditions of the generator.

 Using the tuning criterion (2) allows adaptation to the external conditions of the regulation coefficient with respect to the derivative frequency.

 The measurement and determination of the ratio of the ripple voltage and current of the rotor of the generator in the proposed method meet the criterion of "significant differences".

 The sequence of operations is disclosed by the functional block diagram shown in FIG. 1, where the following notation is adopted: 1 - measurement of the excitation voltage, 2 - measurement of the excitation current; 3-4 - measurement of a variable component; 5 - division operation, 6 - multiplication operation.

The operations are as follows. The voltage (1) and the excitation current (2) are measured, their variable components (3) and (4) are determined, the variable components are divided into each other (5), the result of the operation of dividing σ by the derivative of the frequency f ^{1 is} multiplied (6).

The method can be implemented using a device, the circuit diagram of which is shown in FIG. 2, where 7, 8 are modulators, 9, 10 are demodulators, 11 is a carrier frequency generator (ω _g ) ω _g ≈ 10 ω _k , 12, 13 are low- _pass filters (ω low- _{pass filter} <ω _g ), 14, 15 are band-pass filters (ω _pf = ω _k ), 16, 17 - rectifiers, 18, 19 - smoothing filters, 20 - divider, 21 - multiplier.

The signal U _{f is} supplied to modulator 7, and the signal I _f to modulator 8, the signal from the carrier frequency generator 11 comes to the second inputs of the modulators 7, 8, the signals from the output of the modulators come to demodulators 9, 10, and then through the low-pass filters 12, 13 and bandpass filters 14, 15 to the rectifiers 16, 17, and then through the smoothing filters 18, 19 to the inputs of the divider 20, the output of the divider is connected to one of the two inputs of the multiplier 21, the second input of which receives the signal 8. (56) "Design and study of excitation systems of powerful synchronous machines", L., VNIIelektromash, 1989, p. 74-83.

 USSR author's certificate N 433614, cl. H 02 P 9/14, 1973.

Claims (4)

 1. METHOD FOR AUTOMATIC REGULATION OF EXCITATION OF A SYNCHRONOUS GENERATOR by setting gain factors for deviations and derivatives of voltage and frequency for small oscillations of the generator, increasing gain for the first derivative of the frequency for large oscillations, characterized in that, in order to improve the quality of regulation of excitation of a synchronous generator, the rotor which is powered by a valve converter, measure the ripple voltage and current of the rotor, determine by their ratio of inertia rotor windings and change the gain of the first derivative of the frequency change is directly proportional to the inertia of the rotor winding.  2. The method according to p. 1, characterized in that, in order to improve accuracy, voltage ripple and rotor current are measured at the frequency of the switching cycles of the valve Converter.  3. The method according to PP. 1 and 2, characterized in that, in order to increase reliability, ripple voltage and current of the rotor is measured using the modulation-demodulation operation.  4. The method according to PP. 1 and 3, characterized in that, in order to improve accuracy, the modulation of the signals is carried out at a carrier frequency not less than ten times the frequency of the switching cycles of the valve Converter.

Images